Be Star HD93521

[James Foster]

Here is a recently acquired spectrum of Be star HD93521taken with a CDK17 reflector at f/6.8 with the JTW L-200 spectroscope using the 1800 l/mm grating using the Atik 460ex for a 40 minute exposure; 8x300sec.'s 2x2 binned:


As previous, this was processed in IS and IR corrected against the Miles star HD101606 (F4V).

One thing that I don't understand, when processed with Isis, I get the value SPE_RPOW= 3685 / Spectral resolution power for my R, but when I compute R using the SimSpec_V4_1c_L200.wks speadsheet, my value is closer to 7400, which I used on this chart. It seems like IS is computing my R at half the value it should be.

James

[Robin Leadbeater]

Hi James,

R~ 3700 is indeed unreasonably low for an L200/LHIRES and 1800 grating unless the slit is unusually wide or is out of focus. What is the resolution as measured in the neon lamp spectrum (FWHM of a line?) If the neon lamp is internal to the spectrograph this is normally a good approximation to the true resolution and is how ISIS calculates it.

Cheers
Robin

[James Foster]

To: Robin,

Thanks for the reply!
My slit is 34 microns. Here is a chart showing my Neon lines around Ha, Dispersion is 0.20784831A/px according to Bass 1.96:

Note that I did not use any 2nd or 3rd order averaging of the lines for this file, the is only a map I use when I process in Isis and use manual Ha.lst file I made for my line calibration. For curiosity here are the (RELCO) line calibration numbers for my Ha.lst file for Isis to process:

2
0.20784831
6416.3101 (Ar)
6506.5298 (Ne)
6532.8799 (Ne)
6598.9502 (Ne)
6678.2800 (Ne)

Funny thing is, when I bring in a IS processed spectrum into Bass V1.96, the typical Ha dispersion shown in the bottom info ribbon is 0.01039242 nm/px. Isn't this 1/2 the vale of the above? (0.1039 A/px vs 0.2078 A/px).

James

[Ken Harrison]

James,
You can use the "Measurement options" in BASS project to find the FWHM of one of the neon lines...it also calculates the R value based on that line. This should be used in preference to SimSpec.

fwhm.JPG (38.63 KiB) Viewed 4929 times

[James Foster]

To: Ken,

Thanks! I'll check that out.

James